Air extracting system for hydraulic steering apparatus

Abstract

An air extracting system for a hydraulic steering apparatus which has a pump, a reservoir and a piston-cylinder mechanism which is geared to the steering gear. A two-position changeover valve is positioned in the hydraulic circuit between the pump and the piston cylinder mechanism, which in one position connects them in a closed circuit and in the other position connects the return portion of the hydraulic circuit to the reservoir. The piston has a bore therethrough with a two way check valve therein with a check valve opening element which opens the check valve at the end of the stroke of the piston. When the changeover valve is positioned to connect the return of the hydraulic circuit to the reservoir, when the piston reaches the end of its stroke, the check valve is opened to cause air in the system to pass through the check valve and through the changeover valve to the reservoir.

What is claimed is: 
     
       1. In a hydraulic steering apparatus having a pump means for pumping hydraulic fluid in response to the operation of a steering wheel, a piston-cylinder means having a piston moved in opposite directions and coupled to a steering mechanism for actuating the steering mechanism when the piston is moved, the piston-cylinder means being hydraulically coupled to the pump means, and a reservoir coupled to said pump means, the improvement comprising an air extracting system comprised of a changeover valve coupled between the pump means and the piston-cylinder means for coupling the pump means and the piston-cylinder means in a closed hydraulic circuit when the changeover valve is in one position, and for coupling the pump means to one end of the piston-cylinder means and coupling the other end of the piston-cylinder means to the reservoir when the changeover valve is in the other position, said piston having a bore therethrough from end to end, and two way check valve means in said bore, said check valve means having valve opening means for opening the portion of said check valve means blocking flow through said bore toward said other end of said piston when said piston reaches the end of its stroke toward said other end of said piston-cylinder means, whereby when the changeover valve is in said other position, the opening of said check valve means at the end of the stroke of the piston toward said other end of the piston-cylinder means permits air to be extracted from the piston-cylinder means and directed to the reservoir.   
     
     
       2. The improvement as claimed in claim 1 in which the piston-cylinder means is horizontal and the end of said bore at said one end of said piston is adjacent the top of the piston-cylinder means.